With the Colorado state capitol building visible in the background, partygoers dance and smoke pot during the annual 4/20 marijuana festival in Denver on April 19, 2014. / Brennan Linsley, AP

by Steve Staeger, KUSA-TV

by Steve Staeger, KUSA-TV

DENVER â?? An estimated crowd of 30,000 people packed the Denver Merchandise Mart Saturday for the 2014 Cannabis Cup, kicking off a weekend of marijuana related activities.

The convention is the first held in the city since Colorado legalized recreational pot sales. Inside, vendors showed off new products.

The event kicks off what's expected to be a crowded weekend in the Denver Metro area as people celebrate the first 420 rally since the law changed.

"All the businesses are benefiting in the area," said Bill Bjorncrantz, owner of a medical marijuana supply store in Fort Collins. "We called probably like 50 people trying to get stuff done and in line."

Lines stretched around the convention facility Saturday afternoon, as tickets sold out. A line on I-25 was backed up at 58th Street as people tried to get to the event.

It continues Sunday with more panel discussions about marijuana and more featured products.

"The industry needs to police itself and we need to regulate and put safety measures in place for many of the products," said Rachel O'Bryan with SMART Colorado, a group devoted to keeping children safe from marijuana.

O'Bryan is opposed to the entire weekend of events, as public consumption is against the law. As of about 6 p.m. Saturday, police said on Twitter that 25 people had been cited, 17 of them for public consumption of marijuana.